Since RC19.5, there's a new functionality called "FT User Impersonation":

UltraVNC User's rights on the remote filesystem (server) are the ones of the logged in user.

Typically:
- UltraVNC server must be run as a service
- Users must log into Windows on the UltraVNC server once connected with the viewer (with or without MSLogon)
- A non logged-in user has no access to the server FileSystem
- A logged-in user has the access rights to the remote filesystem corresponding to the actual remote-windows user rights.

Recently, at least 2 PCs I've installed UVNC, when I try tu use the File Tranfer, I got an error: file tranfer is disabled in the remote machine" os something like that, I am sure that its enabled, its possible that versions diferences causes this?
The server runs XP Pro, I tried to configure the VNC Server to run as administrator, that is not the actual user, file tranfer doesnt works, then configured to run as actual user unchecking the virus protection as before, same problem w/ file transfer. somebody can say what I am possible forgetting?